Operation predict problem

[kasyanovse]

Operations may return prediction with different shape: (n_samples, ), (n_samples, n_features), (1, n_samples). It seems that some operations predict are incompatible in ts_forecasting case.

Two problem cases:

1. Combine result of data transform operation with prediction operation in parent node (sometimes).
2. Data transformation operations (sometimes).

If one of problem is fixed then another rises. Both are random.